Wall construction

ABSTRACT

We have found that if we add a polyhydric phenolic compound such as resorcinol to monohydric phenolic resin/cement systems, we can shorten the gel time sufficiently to use the systems in producing walls. The walls generally are cylindrical and serve to confine a liquid. These systems are especially good for producing large diameter, continuous pipe.

This is a division of application Ser. No. 617,353, filed Sept. 29, 1975now U.S. Pat. No. 4,003,173.

This invention relates to cement/phenolic resin systems for thecontinuous production of plastic tubing.

The art has long recognized the desirability of using non-metallicunderground storage tanks to avoid the corrosion which inevitably occursin metal conduits. Glass fiber reinforced synthetic resins such aspolyester resins have comprised the conventional resin systems for thesestorage tanks.

Recently, the industry has been producing these tanks on a mandrelcomprising an endless metal band which is helically wound in abuttingconvolutions about a central support to form a cylindrical formingsurface. U.S. Pat. No. 3,464,879 describes these continuous ribbonforming mandrels. The endless band extends back through the center ofthe support to connect the ends of the helix. The band advancescontinuously to provide a forming surface which both rotates about itsaxis and moves longitudinally along its axis.

FIG. 1 of U.S. Pat. No. 3,886,338 does a particularly good job ofpicturing this continuous ribbon mandrel.

The mandrel is useful for making large diameter tubular structures suchas pipes, tanks, manholes, silos, and the like. The unique design of themandrel makes it possible to produce tubing in continuous or indefinitelengths.

One problem with this process is the short cure times for the resinsystems it employs. These tubular structures must harden quickly becausethe mandrel is continually rotating as well as advancing longitudinally.It is not enough that the materials be solids. They must quickly cure toa hardened mass, especially by the time the continuous pipe reaches theopen end of the mandrel.

To date, we know of no instance where the industry has used phenolicresin/cement systems on such a machine.

We now have discovered that if we add a polyhydric phenolic compound tomonohydric phenolic resin/cement systems, we can shorten the gel timesufficiently to use phenolic resins on these continuous mandrels.

We use the term "polyhydric phenolic compound" to cover polyhydricphenols per se, such as resorcinol, catechol, an hydroquinone and theirsubstitution products and derivatives. While we prefer dihydric phenoliccompounds, we can use trihydric phenolic compounds or copolymerizationproducts of mono, di, and trihydric phenols. We especially preferresorcinol.

The resins we employ are phenol-formaldehyde condensates or phenol-aminocompound-formaldehyde condensates. The amino compounds we employgenerally are urea, melamine, or dicyandiamide.

A detailed discussion of phenol-formaldehyde condensates appears in TheChemistry of Phenolic Resins, Martin, John Wiley & Sons, Inc., 1956, andcited references.

The cements we employ are inorganic cements such as hydraulic cements.Hydraulic cements are powder mixtures made from silica, alumina, lime,iron oxide, and magnesia, which harden when mixed with water. Theyinclude Portland, calcium-aluminate, magnesia, natural, masonry,pozzolan, and slag cements.

We also can employ gypsum with the cements.

To produce a hydrated cement, we can agitate ground cement clinker in awater slurry for a period of time. We then dry the hydrate.

The resin and cement have a weight ratio of resin to cement ranging from1:9 to 9:1 based on the dry weight of cement and the weight of resinsolids.

The amount of water present need only be sufficient to cure the cement.It may be necessary to add additional water or remove some of the waterreaction.

We also can add glass fibers in an amount greater than 0 and up to 60weight percent of molding compound. We can use continuous glass strandor chopped glass fiber or both. Preferably, we incorporate mostlychopped glass fiber with a small amount of continuous strand.

In addition, we can include a silane coupling agent or a mixture ofsilane coupling agents in a total amount of from about 0.01 to about 5percent by weight of molding compound to increase the strengthproperties of the resulting moldings. Particularly suitable silanecoupling agents are "A-1100" and "Tetraethyl Orthosilicate,"commercially available from Union Carbide Corporation. A-1100 isgamma-aminopropyl-triethoxysilane and Tetraethyl Orthosilicate istetraethoxysilane.

With regard to the continuous production of tubing, we generally employa particulate filler such as sand. The amount of filler ranges from 0 to150 parts of sand per part of molding compound.

The mole ratio of the polyhydric phenolic compound to the phenol in theresin ranges from 1:10 to 10:1. Preferably, this ratio ranges from 1:4to 10:1.

In the cylindrical wall construction of this invention, thethermosetting resin matrix comprises from 30 to 40 weight percent of thewall, glass fibers comprise 10 to 20 weight percent of the wall, and thefiller comprises 20 to 50 weight percent of the wall.

The FIGURE shows an endless ribbon mandrel for the continuous productionof plastic tubing. The FIGURE also shows the use of this invention inassociation with the mandrel.

The endless mandrel 10, shown in the FIGURE, comprises an endless steelband 12 which recirculates about a core 14. The core is supported at thehead of the machine 18, which also includes a drive 19 for the mandrel.The core is not supported at the opposite end. The major portion of theband is helically wrapped in abutting convolutions 15a and 15b aroundthe periphery of the core to form a generally smooth forming surface onwhich materials can be applied. The band advances from the supported endof the core to the free end where it passes back through the center ofthe core to the supported end.

A continuously formed cylindrical wall 20 is built on the mandrel 10from a combination of chopped glass fibers, a particulate filler, andresin. The sand or other pulverulent filler is fed from an overheadhopper 36 having a downwardly directed opening 38. The chopped glassfibers are supplied from continuous glass filaments 39 to a chopper 40.Thermosetting resin is fed from a conventional resin sprinkler 42 havinga plurality of downwardly opening apertures.

It will be appreciated that the concurrent supply of resin 56, choppedglass fibers 58 and sand 60 to the surface of mandrel 10 will result inthe build up of successive layers of each material as the mandrelsurface advances. The resin impregnating the glass and sand andembedding the glass and sand in a resin matrix.

The method of this invention includes the steps of applying a filler(sand and cement) to a continuously rotating cylindrical form,distributing glass fibers in random orientation and then adding theresin and polyhydric phenolic compound while continuing the rotation ofthe form, and heating the cylindrical wall to cure the thermosettingresin. The resultant cylindrical wall is able to withstand thesubstantial forces encountered in underground installation and avoidscracking or the building of stresses encountered in curing of thethermosetting resin.

The mandrel rotates at approximately 5 RPM's. The steel band moves fromleft to right for each revolution of the mandrel. Each of the threeapplicator stations is approximately 11 band widths wide so that thefinished product contains 11 layers. These systems are especially goodfor producing large diameter, continuous pipe.

U.S. Pat. No. 3,871,409 describes this method more completely.

If desired, the molding compounds of our invention also can beincorporated into either a sheet molding compound (SMC) or a bulkmolding compound (BMC), which contain glass fibers. We cure theresulting molded articles with or without glass fibers in a hot air ovenby conventional means. Or, if the systems cure themselves, no heating isnecessary.

The following examples further illustrate our invention.

EXAMPLE I

In a typical method of this invention such as we just described, we atthe first station applied a mixture of 70 parts by weight of sand and41.1 parts by weight of Portland cement to the continuously rotatingcylindrical form. At the next station, we applied 70 parts by weight ofchopped glass fiber (E glass). At the third station, we applied amixture of 9.4 parts by weight of phenol and 17.3 parts by weight of 52%formaldehyde. We then heated the mandrel to cure the system.

The reaction gelled after 53 minutes.

EXAMPLE II

We repeated the procedure of Example I except that we employed 2.20parts by weight of resorcinol and 7.52 parts by weight of phenol insteadof the 9.4 parts by weight of phenol.

The reaction gelled after 53 seconds. The mole ratio or resorcinol tophenol was 1 to 4.

EXAMPLE III

We mixed 9.4 grams (0.1 mole) of phenol, 17.3 grams (0.3 mole) offormaldehyde, and 41.1 grams of Portland cement together in a beaker.The reaction gelled after 53 minutes. We made other mixtures like thisone except that we employed various mole ratios of resorcinol andphenol. The results were as follows:

    ______________________________________                                        Moles of Resorcinol                                                                         Moles of Phenol                                                                              Gel Time                                         ______________________________________                                        0             0.1             53 minutes                                      0.005         0.095          35 minutes                                       0.01          0.09           29 minutes                                       0.02          0.08           53 seconds                                       0.03          0.07           39 seconds                                       0.04          0.06           36 seconds                                       0.09          0.01           10 seconds                                       ______________________________________                                    

These examples clearly show that we can use polyhydric phenoliccompounds to accelerate the gel time of our phenolic/cement system.These systems are especially good for producing large diameter,continuous pipe.

We intend to include modifications and variations within the scope andspirit of our invention.

We claim:
 1. A method for producing a cylindrical wall comprising thesteps of:(a) applying a filler and cement to a continuously rotatingcylindrical form; (b) distributing glass fibers in random orientationand then adding phenol, formaldehyde, and at least one polyhydricphenolic compound alone or combination with an amino compound whilecontinuing the rotation of the form; and (c) curing the resin.
 2. Amethod according to claim 1 wherein the polyhydric phenolic compound andthe phenol have a mole ratio of polyhydric phenolic compound to phenolranging from 1:10 to 10:1.
 3. A method according to claim 2 wherein themole ratio of polyhydric phenolic compound to phenol ranges from 1:4 to10:1.
 4. A method according to claim 1 wherein the polyhydric phenoliccompound is resorcinol, catechol, or hydroquinone.
 5. A method accordingto claim 1 wherein the polyhydric phenolic compound is resorcinol.